Cytogenetic and molecular techniques have advanced our knowledge of the biologic basis of cancer, particularly in the pediatric neoplasms. Information for pediatric brain tumors has been limited, due to technical problems and limited access to specimens. I. Using several methods we will prepare karyotypes from a describe the chromosomal abnormalities in a series of pediatric brain tumors. This will involve cytogenetic analysis of tumor and normal tissue from the same individual. Our studies will include analysis of direct preparations from tumors, short term tissue culture of tumor specimens, xenografts of selected tumors propagated in nude mice as well as short term peripheral blood cultures to determine the constitutional karyotype of the affected individual. II. We intend to determine whether there are molecular changes which correlate with the consistent abnormalities observed in subsets of these tumors. We will perform comparative Southern blot analysis of tumor and normal DNA to look for presence of and potential conversion to homozygosity for chromosome specific probes implicated in the tumors. Initial studies will focus on chromosome 17. We can also perform Southern blot analysis of tumor cell DNA to look for evidence of oncogene amplification if HSRs or DMs are present, or PFG electrophoresis to detect oncogene rearrangement due to transposition if translocations are present. III. We will propagate selected high grade pediatric brain tumors as xenografts in the nude mouse to facilitate cytogenetic analysis and to expand the tumor mass available for molecular study. We propose to compare karyotypes obtained from cytogenetic analysis of tumors propagated in the mouse with those observed in direct preparations or form short term culture of the tumor. As we begin to understand the functional consequences of genomic alterations, by identifying the genes involved and the mechanisms by which they exert their effect, we will be able to translate this information into improvements in diagnosis and therapy.